In conventional hemodynamic pressure sensing and monitoring systems, a catheter from the heart or other location is connected to a tubular manifold and frame assembly which is provided with one or more valved ports. Flexible plastic tubing extends from the manifold ports of the assembly (which is typically attached to the patient's arm, chest, etc.) to one or more pressure sensor and monitoring devices. Each pressure sensor includes a transducer dome and transducer, typically mounted on a vertical post located about six feet away from the patient. In this arrangement, blood passing into and/or through the manifold may be periodically diverted via conventional petcock type valves through a pressure monitoring tube connected between one of the manifold ports and the post-mounted pressure sensor.
However, this arrangement is not completely satisfactory for a number of reasons. Most significantly, the frequency response or resolution of the pressure readings are affected by the length and durometer of the pressure monitoring tubing, the composition of the tubing and so on. In other words, any distortion or change in flexibility of the tubing (which is normally constructed of a flexible plastic material) as a result of temperature changes, for example, will impact on the accuracy of the pressure readings. As a result, the apparatus must be re-calibrated often to compensate for such changes.
A further requirement to obtain accurate readings is that the transducer must be mounted at substantially the same height as the patient to avoid the effects of gravity. This requirement necessitates additional equipment which permits the pressure transducer to be vertically adjusted on the pole or stand.
The above-described conventional systems require periodic manipulation of the manifold petcocks when readings are desired. This, of course, presents a danger of leakage and resulting contamination of persons and/or things in the immediate area.
The present invention provides a method and apparatus which eliminates the aforementioned problems associated with conventional hemodynamic pressure monitoring systems.
In an exemplary embodiment of the present invention, a pressure sensing transducer is mounted directly within the manifold assembly. The transducer includes a microchip enclosed within a gel, effectively directly exposed to blood flowing into the manifold. This construction has many advantages, one of which is the ability to continuously sense and monitor pressure. The chip itself is preferably permanently joined and sealed to the manifold, and connection means are provided so that an electrical cable, connected to a monitor, can be easily connected or disconnected from the manifold assembly. In this regard, an O-ring seal is preferably employed between the transducer chip and the manifold to prevent the escape of fluid from around the sensor.
The transducer per se is not part of this invention and, in a preferred embodiment, is a microchip sensor commercially available pressure sensor manufactured by Motorola, the details of which are specified herein. This invention relates to the arrangement of the sensor within a manifold assembly, such that pressure may be continuously sensed and monitored without danger of leakage.
As noted above, the present invention has numerous advantages over prior art pressure sensing systems. For example, the present invention provides a simple, easy to use, highly accurate and significantly less costly pressure monitor which eliminates the conventional transducer dome and pressure monitoring tubing.
In addition, since the manifold including the sensor may be attached directly to the patient, the concern for the effects of gravity, is substantially eliminated.
Another advantage lies in the fact that the time consuming recalibration efforts caused by changes in the plastic monitoring tubing, primarily as a result of temperature changes, are also eliminated. In this regard, the preferred microchip sensor includes an automatic temperature compensation and recalibration circuit so that, to the extent periodic calibration is required, it is done automatically.
The present invention also confines the blood within the manifold, thereby reducing the risk of contamination present in prior art systems where the blood must flow through the lengthy monitoring tube to reach the post-mounted sensor.
Another advantage of the present invention is that the entire assembly, including the transducer, is easily disposed of after each use.
It will be appreciated that the sensor/manifold arrangement of this invention may be incorporated into a single port manifold, or in a multi-port manifold where one or more of the remaining ports may contain conventional valving arrangements. Of course, one or more of the additional ports may also incorporate the sensor in accordance with this invention.
Thus, the present invention in accordance with one embodiment comprises a disposable transducer manifold assembly for hemodynamic pressure monitoring comprising:
a manifold frame; PA1 a hollow, tubular manifold formed within said frame and having an inlet at one end for receiving fluid; PA1 at least one sensing port provided in the tubular manifold; PA1 a pressure sensing transducer mounted adjacent the port, a sensing surface of the transducer adapted for direct exposure to fluid in the tubular manifold; and PA1 connector means extending from the pressure sensing transducer. PA1 providing a tubular manifold having an inlet at one end and at least one sensing port; PA1 permanently securing a pressure sensing transducer directly to the manifold such that a pressure sensing surface of the transducer is exposed directly to blood in the manifold through the sensing port; PA1 sealing the pressure sensing surface relative to the manifold; and PA1 providing electrical cable means for connection between the manifold and a monitor device.
In a related aspect, the present invention provides a method for continuously monitoring blood pressure comprising the steps of:
Additional objects and advantages of the present invention will become apparent from the detailed description which follows.